The PixFEL front-end for X-ray imaging in the radiation environment of next generation FELs

In the framework of the PixFEL project, a processing channel for pixel sensor readout has been designed and fabricated in a 65 nm CMOS technology. The detector under development is aimed at applications to coherent X-ray diffraction imaging (CXDI) at the next generation free electron lasers (FELs). Especially in the detector region around the hole for the unscattered photon beam, pixels will be subjected to huge doses of ionizing radiation, in the order of tens of Grad(SiO2, during their lifetime. The total ionizing dose (TID) for the frontend electronics, while significantly reduced by the shielding effect of the detector, is still expected to exceed one Grad(SiO2. This paper investigates the performance degradation in the PixFEL readout circuit, in particular in the charge sensitive amplifier, after exposure to X-ray doses up to 100 Mrad(SiO2).